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THE POPULAR SCIENCE MONTHLY. 



Then the clover that had been thrown away 

 attracted their attention, and they ate greed- 

 ily even of that which was musty. A small 

 extemporized silo was tentatively made, in 

 the natural ground where it was well 

 drained, without walling, and was filled 

 with green clover. The ensilage came out 

 in perfect condition and entirely palatable. 

 The result of the last experiment shows 

 how persons living where the subsoil is very 

 compact might make a silo with either very 

 light walls or with none at all. 



How Oolite may be formed. Mr. F. 



W. Putnam, in giving an account of a visit 

 he made some months ago to the Mammoth 

 Cave, remarks that in one of the newly 

 discovered chambers he noticed that many 

 fragments of stalactites and small pieces 

 from the walls of the cave, which had fallen 

 into a little pool, were worn round and 

 smooth by constant attrition, occasioned by 

 the dropping of water from the high ceiling 

 of the chamber. Should the water cease 

 to drip in this place, as it probably will, 

 and that in the pool evaporate, leaving the 

 lime to crystallize about these small peb- 

 bles, a conglomerate would be formed which 

 would have some resemblance to oolitic 

 limestone, pebbles of which occurred in the 

 pool, probably derived from fragments de- 

 tached from the walls of the chamber. 

 Calling attention to the formation of " cave 

 pearls," which he had found in Grand 

 Avenue Cave some years ago, he remarked 

 that should such a mass of small pearl-like 

 lime-concretions as were found in the last- 

 named cave ever be cemented together, the 

 resemblance to oolite would be very marked. 

 "While he did not wish to be understood as 

 stating that the oolitic limestone was formed 

 in this way, he could not help thinking that 

 a rock of similar appearance might be lo- 

 cally so produced under the conditions he 

 had observed. 



Lead in Food and the Indnstrial Arts. 

 M. Armand Gautier has recently published 

 a memorandum on the dangers arising from 

 the use of lead in food-vessels and in vari- 

 ous arts, and on the means of counteracting 

 them. He shows that lead may be detected 

 in preserved vegetables, fish, lobsters, meats, 

 in drinking-water, and water artificially 



charged with carbonic acid, in acid foods 

 and drinks preserved in glass vessels, in tin 

 dishes, in the coverings of our walls and 

 furniture, in the leather of our boots, in our 

 dishes, and in our glazed table-cloths. He 

 gives a simple and practical test for the 

 presence of lead in solder or tinned or 

 solid metal, and for estimating the propor- 

 tion of the poison that may be there. It 

 consists in turning on two drops of acetic 

 acid upon the surface of the metallic ob- 

 ject, allowing it to evaporate in the air, then 

 touching with a solution of chromate of 

 potash, letting dry, and washing with water. 

 The yellow chromate of lead, thus obtained, 

 adheres to the metal, and does not change 

 color for several days, so that the spot can 

 be kept in evidence. "When a tin thus 

 treated shows a yellow spot it should be re- 

 jected ; if it is used in a food-can the con- 

 tents should be regarded as suspicious, even 

 if the soldering has all been done on the 

 outside, as the latest regulations require. 

 The general use of food preparations done 

 up in metallic boxes that are soldered with 

 an alloy of lead necessarily results in the 

 introduction of a little lead into the econ- 

 omy, and, according to M. Gautier, the 

 proportions of lead thus absorbed, gener- 

 ally very weak with vegetables, are much 

 stronger in foods rich with fats, and espe- 

 cially in fish preserved in oil ; the oils that 

 surround the fish are still more strongly 

 charged with it ; and preserved meats con- 

 tain it in widely varying proportions. The 

 lead" appears to exist in vegetables in the 

 shape of an albuminate soluble in the acids 

 of the stomach, in fat-substances as an 

 oleate and a palminate dissolved in the fats, 

 and absorbable with them when they un- 

 dergo emulsion in the digestive tube. The 

 use of lead in a multitude of arts and 

 trades, too numerous to be named here, 

 leads to more perceptible and extensive 

 poisoning than the minute quantities of the 

 metal that reach us through our foods and 

 food-vessels, the importance of which is 

 indicated by the admission of an average 

 number of seven hundred workmen suffer- 

 ing from it to the hospitals of Paris every 

 year. The compounds of lead with which 

 these workmen come in contact are absorbed 

 by the skin, the mouth, the nostrils, and in 

 breathing. To workmen exposed to such 



